Punching machine

ABSTRACT

A PUNCHING MACHINE HAS A RAM DRIVEN BY A FLUID PRESSURE ACTUATOR WHICH IS POWERED BY TWO HYDRAULIC PUMPS, THE OUTLET OF ONE PUMP HAVING A RELIEF VALVE WHICH RELIEVES BEFORE PUNCHING PRESSURE IS REACHED AND WHICH IS ISOLATED FOM THE FLUID ACTUATOR BY A CHECK VALVE, SO THAT THE RATE OR RAM MOVEMENT IS REDUCED BEFORE MAXIMUM PUNCHING PRESSURE IS ATTAINED. THE OTHER PUMP OUTLET HAS AN IN-LINE RELIEF VALVE, UPSTREAM OF WHICH RELIEF VALVE THERE IS CONNECTED FLUID-PRESSURE ACTUATED WORKPIECE HOLD DOWN MEMBER.

NOV. 30, 1971 A KRYNYTZKY ETAL 3,623,389

PUNCHING MACHINE Original Filed Nov. 14, 1966 r//N/r Sabo/Vy O/o Hoffman/7 M, @I

United States Patent O 3,623,389 PUNCHING MACHINE Alexander Krynytzky, West Seneca, N.Y., Arthur K.

Schott, Greensboro, N.C., and Otto Hoffmann, Tonawanda Township, Erie County, N.Y., assignors to Houdaille Industries, Inc.

Original application Nov. 14, 1966, Ser. No. 596,384, now Patent No. 3,529,502, dated Sept. 22, 1970. Divided and this application May 25, 1970, Ser. No. 41,143

lut. Cl. B26d 5/12 U.S. Cl. 83-617 6 Claims ABSTRACT OF THE DISCLOSURE A punching machine has a ram driven by a fluid pressure actuator which is powered by two hydraulic pumps, the outlet of one pump having a relief valve which relieves before punching pressure is reached and which is isolated from the iuid actuator by a check valve, so that the rate of ram movement is reduced before maximum punching pressure is attained. The other pump outlet has an in-line relief valve, upstream of which relief valve there is connected a huid-pressure actuated workpiece hold down member.

rlhis application is a divisional application for our copending application for U.S. patent on a Punching Machine, led Nov. 14, 1966, Ser. No. 596,384, now U.S. Pat. No. 3,529,502.

This invention relates generally to punching machines, and more specifically the invention relates to a heavy duty punch press.

The present invention relates to novel features and novel combinations of features which enable the punching of workpieces of relatively great thickness, whereby high punching and stripping forces are required. To that end, a novel drive system is provided which includes means for holding the workpiece during punching thereof, and during the stripping of the workpiece from the punch. Accordingly, it is an object of the present invention to provide a heavy duty punching machine.

A further object of the present invention is to provide means for reciprocating a punch tool while avoiding lengthy drive structures, such means being able to be inched or jogged in small increments if desired.

A still further object of the present invention is to provide a punching machine having adjustable capacity and thereby having overload protection.

Yet another object of the present invention is to provide a punching machine wherein the amount of space between the punch and the die when the punch is retracted can be adjusted.

A still further object of the present invention is to provide a hydraulic operating system by which the magnitude of holding and stripping forces applied to the workpiece is in accordance with the need in any particular stroke.

Yet another object of the present invention is to provide a punching machine wherein the movable tool is driven with a fast approach, is driven comparatively slowly during punching, has a fixed predetermined shut height, and wherein the movable tool is driven relatively rapidly during retraction or return.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and to the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

The single drawing is a schematic diagram of the fluid system employed with the diagrammatically illustrated upper portion of the punching machine.

As shown on the drawing:

The principles of this invention are particularly useful when embodied in a punching machine such as is schematically and diagrammatically illustrated in the drawing. The punching machine includes a rigid frame, diagrammatically illustrated at various points and which, when viewed from the side, is of C-shaped configuration having an upper arm 12 and a lower arm 12a rigidly secured thereto which supports a lower xed tool, here comprising a die tool 13. The upper arm 12 slidably supports a ram 15, at least one and preferably a pair of clamping actuators 17, 17, a toggle link or linkage 18, a fluid actuator 119, and a pair of electrical switches 20, 21.

The ram 15 supports an upper movable tool, here comprising a punch tool 22 for coacting with the die 413 on a workpiece. A removable upper tool holder (not shown) slidably supports a hold down member 24. The removable upper tool holder 16 is substantially the same as that shown in U.S. Pat. No. 3,225,636 to which the reader is referred for further structural information.

The ram 15 is slidably guided by the frame for vertical movement and includes a pair of ears 28, 28, each of which is provided with an opening 29 which extends parallel to the direction of ram reciprocation. At its lower end, the ram 15 is provided with an adapter which directly supports a head or driver of the punch tool 22. In this embodiment, the adapter and the punch head are provided with a positive connection therebetween in the form of a horizontally extending T-slot 32 and a T-head 33 received therein. The direction in which the horizontal T-slot 32 extends is such as to freely engage and disengage the positive connection 32, 33 in response to removal or attachment of the upper tool holder 16.

The clamping actuators I17 respectively include a hollow cylinder 35 which comprises a cavity, a pistou 36, and a tubular rod 37 having a shoulder 38. The interior of the tubular rod 37 communicates with the interior of the hollow cylinder 35, which has no liuid port of itself. Thus, Huid pressure may be applied through the tubular rod 37 to act on one end, here the upper end, of the piston 36. The piston 36 includes means at one side, here the lower side, to act on the hold down member 24. In this embodiment, such means merely comprises a pushing surface, which may be of any convenient configuration. At the other side of the piston 36, means are provided to deliver power to the piston 36 from the ram for retraction of the piston 36. Such means comprises the tubular rod 37, the upper end of which not only is uidly connected to the supply of pressurized iluid, but which supports the shoulder 38.

The toggle link 18 is pivotally supported at its upper end by an upper pivot pin 40 carried by the upper arm 12, while the ram 15 has a pivotal connection with a lower pivot pin 41 carried by the lower end of the toggle link 18. The toggle link 18 includes a central pin 42, secured to one of the links 43 and supporting the other link 45. The central pin `42 is also secured to the piston rod 54 of the hydraulic or uid actuator 19.

The hydraulic actuator 19 at its rod end is provided with a trunnion 55 which is pivotally supported on the upper arm 12. As the fluid actuator 19 is reciprocated from the position shown in solid lines to the position shown in dashed lines, the actuator 19 pivots when the links are aligned, the right end as illustrated going slightly up, the actuator going back to the position illustrated when the links have passed a like distance beyond the other side of center.

The switches 20, 21 have actuators and are so disposed that the link 43 operates the switch 21 when the piston rod 54 is retracted, and operates the actuator of the switch 20 when the piston rod S4 is extended. The switches 20, 21 may be of any known type and are adjustably mounted so that the `amount of travel of the piston rod 54 from a central position wherein the axes of the pins 40, 41, 42 are in alignment with each other, may be selected. The switches 20, 21 are connected electrically in the circuit that provides fluid power to the hydraulic actuator 19 to terminate the admission of further pressurized nid thereto by opening the circuits to a 4way valve in the uid system described below.

The lower end of the pistons 36 move the hold down member 24 downwardly against the force of springs (not shown) to engage the workpiece, thereby clamping it against the die 13. When the clamping act-uators 17 are retracted by the ram 15, the springs restore the hold down member 24 to the position illustrated.

The hold down member 24 has an internal surface which serves to guide the upper tool, in this case, the punch tool 22.

The fluid system for the actuators 17, 17, 19 is generally indicated by the numeral 72. In the illustrated form of the system 72, a pair of constant delivery hydraulic pumps 73, 74 is driven by an electric motor 75. The pumps 73, 74 have inlets connected to a sump 76 to which used fluid is returned or vented at various points diagrammatically illustrated. The pump 73 has ya typical capacity of 37 gallons per minute, and its output is conducted through a check valve 77 to a 3-position 4-way valve 78. The 4-way valve 78 is self-centering, as by springs, and in the centered position, the entire output of the pump 73 is returned to the sump. Connected between the pump 73 and the check valve 77'is a relief valve 79 which typically is set to return fluid at 1000 p.s.i. under conditions described below. The pump 74 has a typical capacity of 12 gallons per minute, and its outlet is connected through an in-line relief valve 80 to the inlet of the 4-way valve 7 8.

The fluid actuator 19 is of the double-acting type, and has a typical piston diameter of six inches. Opposite sides of its piston are connected by hydraulic lines 81, S2 to the actuator portions of the 4-way valve 78. A portion of each of the lines 81, 82 comprises exible hose which ilexes in response to pivoting of the actuator 19 about the axis of its trunnion 55.

The pump 74 has its outlet also connected by a line 83 to the clamping actuators 17, 17, and as the connection is made through the tubular rods 37 which move, the line 83 also includes iiexible hose portions to accommodate such movement. The outlet of the pump 74 is also connected by a line 84 to an unloading valve 85, A typical unloading valve for this purpose is a Vickers C2-8l5-S3. In the drawing, an equivalent diagram has been provided to show that the unloading valve 85 normally conducts hydraulic uid therethrough without appreciable resistance, the outlet thereof being connected through a reliet` valve 86 to the sump. The relief valve 86 has a typical cracking pressure of about 20 p.s.i., and the presence of at least such pressure is sensed by an electrical pressure switch 87 which is electrically connected with the actuating solenoids of the 4-way valve 78. Thus, the `fluid actuator 19 and the ram 1S cannot -be actuated unless fluid pressure is available to operate the clamping actuators 17. When the unloading valve y85 is electrically energized, which normally takes place simultaneously with energizing of one of the solenoids of the -4-way valve 78, the low resistance path through the unloading valve 85 is blocked, thereby enabling fluid pressure to build up in the clamping actuators 17. The unloading valve 85 includes an adjustable relief valve portion indicated at 88 which typically would be set to relieve pressure `at 2000 ps.i., thereby adjusting the ultimate tonnage capacity of the press. For instance, if the punch 22 should jam, the maximum force that could be applied would be limited by the setting of the relief valve portion 88. lf ,it i desired i0 Set hS VVC below 1000 p.s.i., corresponding adjustment of the relief valve 79 is also required. A

To operate the punching machine, the solenoid of the unloading valve 85 is energized along with one of the solenoids of the 4-Way valve 78. The pump 73 delivers fluid to one side of the iluid actuator 19, while the pump 74 supplies pressurized duid to the clamping actuators 17. The clamping actuators 17 each have a typical piston diameter of 2% inches, and the typical values mentioned herein enable the punch ram 15 and the hold down member 24 to move downwardly together. However, it is preferred that the capacities, sizes, restrictions and the like in the system be `such that rm clamping kof the workpiece is obtained before the punch 22 engages the workpiece. As the hold down member 24 clamps against the workpiece, the line pressure builds up above the cracking pressure of the relief valve 80, thereby delivering fluid from both of the pumps 73, 74 to the uid actuator 19 at a relatively fast rate, thereby building up a pressure in the uid actuator 19 for effecting punching. In the event that the punching pressure exceeds the setting of the relief valve 79, further pressure increase is provided solely by the pump 74 so that a slower increase of pressure is provided immediately prior to punching. Upon completion of the actual punching, the pressure in the actuator 19 drops sharply, thereby reclosing the relief valve 79, whereupon both of the pumps 73, 74 continue to deliver fluid to the liuid actuator 19 to drive it through center and to the other end of its travel as determined by the switch 20 or 21. As the toggle link 18 passes center, it begins to retract the ram while uid pressure is still exerted on the hold down member 24. Subject to the pressure drop produced by the relief valve 80, the pressure in the fluid actuator 19 is substantially the same as that in the clamping actuators 17 If the workpiece produces a heavy drag on the punch 22 and resists being stripped from the punch 22, such condition will cause the pressure to build up in the actuator 19, and will `cause a corresponding build-up of uid pressure in the clamping actuators 17. Such pressure build-up increases until the necessary force is produced to strip the workpiece from the punch. After the stripipng has been completed, the cross bar or ears 28 of the ram 15 will engage the abutments 38 on the clamping actuators 17 and will restore them, retract them or return them to the uppermost position, forcing tluid out of the clamping actuators. By this action, the fluid actuator 19 overpowers the fluid actuators 17 The system controls are so arranged that the solenoids that were energized will then be deenergized, and when the next punch signal is provided, the solenoid of the unloading valve 85 wil be energized with the other of the solenoids of the 4-way valve 78. This reverses the action of the uid actuator 19, but the action of the ram 15 and the clamping actuators 17 will be the same. Thus, a complete punching cycle with the ram going down and going up is produced by each motion of the `fluid actuator 19.

In the event that a conventional upper tool holder is employed which does not have the hold down member 24, the downward movement of the clamping actuators 17 will be limited by the shoulders 38, and the fluid system would otherwise operate in the manner described. In such operation, the press ram 15 stores stripping energy in springs that form part of such other tool assembly in a conventional manner. However, the apparatus disclosed herein is particularly advantageous over such prior apparatus in that much higher holding and stripping forces can be developed than can be provided in the same space by such prior structures, while being interchangeable therewith. By this change of structure, it has been possible to increase tonnage capacities of presses from Z50-ton to -ton.

Although various minor modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon al1 such embodiments as reasonably 5 6 and properly come within the scope of our contribution to 4. A punching machine according to claim 1, in which the art. said relief valve vents its fluid to a sump.

We claim as our invention: 5. A punching machine according to claim 1, including: 1. A punching machine, comprising in combination: (a) an in-line relief valve through which fluid from (a) a frame; 5 only said other of said pumps ows; (b) a ram supported ey said frame for reciprocating a (b) a fluid pressure actuated workpiece hold down punch tool with respect to a die tool; member; and (c) a iluid actuator carried by said frame and con- (c) a 'luid line connecting said hold down member to nected to reciprocably drive said ram; said other of said pumps at a point upstream of said (d) a pair of hydraulic pumps connected to deliver 10 in-line relief valve.

pressurized fluid simultaneously to said actuator; 6. A punching machine according to claim 1 in which (e) a relief valve connected to the outlet of one of said said other of said pumps has a lesser volumetric capacity pumps for venting uid at a pressure below that than said one of `said pumps, whereby the rate of ram needed for punching; and movement is at least halved during application of maxi- (f) a check valve isolating said relief valve from the 15 mum Punching forceother of said pumps; whereby both of `said pumps provide iiuid for all actuator References Cited movement except during application of maximum punch- UNITED STATES PATENTS nlhf when only said other of said pumps provides 2 2,092,092 9/1937 Sinclair et al 81,) 617 X 0 2,532,672 12/1950 Michael et al. 83-630 X 2. A punching machine according to claim il., including a sump common to the inlets of said pum s.

3. A punching machine according to laim l, including JAMES M' MEISTER Primary Examiner a 4-way valve having an inlet connected to receive pressurized uid from both of said pumps, and actuator ports 25 U'S' C1' X'R' connected to opposite ends of said fluid actuator, said 83T630: 639 fluid actuator being of the double acting type. 

